Antimicrobial films and sponge cloths are already known. Likewise, antimicrobial tubular films are known which are used as food casings. This applies in particular to ready-to-fill premoistened cellulose fiber skins. These typically have a moisture fraction of from 20 to 40% by weight, based on their total weight. In addition, US 2007/0020366 A1 describes shrink-wrap plastic bags that are sprayed or impregnated with antimicrobial agents such as acid calciumsulfate (ACS) or lauramide arginine esters, especially ethyl lauroylarginate hydrochloride, in order to preserve, for example, ham.
Food casings based on polysaccharides or coated textile materials for sausage products having a moisture content greater than 20% that must be kept mold-free for soaking-free processing, may be made germ free:
a) by preparations containing fungicidal substances, such as sorbic acid, benzoic acid, propionic acid, esters of para-hydroxybenzoic acid or salts thereof (as described in U.S. Pat. No. 2,979,419),
b) by reducing the water activity (aw) below 0.94 with glycerol and/or propanediol (as described in DE 2721427, whose United States equivalent is U.S. Pat. No. 4,867,204) or
c) by sterilization before packaging by irradiation with gamma rays, or treatment with oxidizing agents (H2O2, peroxides).
It is substantially more complicated to produce food casings for sausage products whose casings must remain reliably mold-free after processing, i.e. after soaking, stuffing and cooking or scalding even in the case of dry or semidry sausage or scalded-emulsion sausage or cooked-meat sausage.
For this purpose sorbic acid or poorly soluble fungicides such as glycerol monolaurate (EP 0 141 066, whose United States equivalent is U.S. Pat. No. 4,662,403) or isothiazolones (EP 0 330 996, whose United States equivalent is U.S. Pat. No. 4,940,615) bound in the manner of salt to polyamine-polyamide-epichlorohydrin resins (DE 32 40 847, whose United States equivalent is U.S. Pat. Nos. 3,617,312 and 2,979,419) or to casein/glyoxal coatings (EP 0 263 434) are known. The most effective preservation, however, was achieved with dimethyldidecylammonium chloride. The ammonium ions enter into an ionic bond with anionic groups such as, for example, with the carboxylate groups of the cellulose or the collagen (in the case of collagen-coated textile skins) or the amino groups of the polyamide or collagen. A slow-release action is achieved in this manner.
Cellulose sponges and cellulose sponge cloths which are softened, for example, with a moisture content of at least 70% may be kept mold-free when packaged up until use, for example by means of the abovementioned fungicidal substances or by sterilization with gamma rays or peroxides. It is substantially more difficult to maintain biocidal protection of cellulose sponges and cellulose sponge cloths after they have been repeatedly washed.
Alkyldimethylbenzylammonium chloride has proved to be an effective fungicide having slow-release action which can be removed only slowly by water, owing to the substantive attachment of the ammonium group to cotton fibers, which are used as internal reinforcement of the sponge cloths.
The preparations containing unbound readily soluble fungicides and bactericides, as mentioned under a), the methods according to b) and c), the application by simple spraying onto plastics surfaces, such as shrink-wrap bags, and also the preparations containing Resamin, casein sorbate, glycerol monolaurate or isothiazolones do not offer sufficient protection at high moistures, heavy contamination or relatively heavy germ pressure, especially in the case of dry or semidry sausages and scalded-emulsion sausages. At a relatively high spore pressure, e.g. during ripening of dry or semidry sausages, in addition to mold-ripened dry or semidry sausages or during the storage of twice-packaged scalded-emulsion sausages, they are completely unsuitable.
At a very high spore pressure and very long storage time under extreme conditions, a preparation containing dimethyldidecylammonium chloride is also not safe enough, in particular in the case of long soaking of the casings before stuffing and at a low application rate.
US 2009/0023790 A1 discloses antimicrobially active compositions which comprise a) N-methyl-1,2-benzoisothiazolin-3-one and b) at least one further microbiocide. The further microbiocide is ethyl lauroyl arginate hydrochloride (LAECl), cocamidopropyl-N-2-hydroxy-ethylcarbamoylmethyldimethylammonium chloride, Cu(II)-2-aminoethanolate and didecyldimethylammonium chloride, didecyldimethylammonium carbonate and bicarbonate, Cu(II)-aminoethanolate, glycerol monolaurate, propylene glycol monolaurate or propylene glycol caprylate. The compositions prevent the growth of microorganisms on a multiplicity of products including food packages made of plastic or paper, and wiping cloths. However, they can be extracted by washing and thus rapidly lose activity since they are not firmly bound to the support.
In the case of cellulose sponges and cellulose sponge cloths, for example, the preparations under a) and c) lead to mold and bacterial infection on repeated use. Also the action of the preparations containing alkyldimethylbenzylammonium chloride or isothiazolones decreases gradually with increasing extraction processes by washing.